Two problems with leading. Which
suit and which card? The latter is easier.

This is about your first lead,
but much applies later in the play as well

1.Standard leads
against any contract

Top of sequence , but care if
highest card is 10 or less

Low card from single honour

Middle card (7-10) from ‘poor’ suit

1(i)Against suit contracts: do
not under-lead an ace, and try not to under-lead a K, do not lead from a broken
suit like AQ. Try not to lead a singleton trump unless opponent’s are expected to hold 10 or more trumps
between their two hands. A low card lead from Kxx in trumps very rarely costs!

If partner has bid:

Lead highest card of partner’s
suit

Lead a singleton or doubleton in
an un-bid suit only if you have reasonable trumps and the clear expectation
that partner can gain the lead.

If you have supported partner’s suit: always lead an ace, otherwise as
standard leads

(ii)Against no-trumps: you may
lead from an honour in an un-bid
suit. Lead 4th highest from an un-bid suit containing an honour

(ii) If partner’s suit bid has been overcalled 1NT, and if
you hold a singleton in partner‘s suit, lead a more solid suit e.g. QJ10x than the singleton

(iii) Against a slam do not
under-lead an ace or K. Lead trumps if necessary. Avoid cashing an ace, unless
you expect to win a trick in another suit.

2. Which suit?

You often have
to make choices that give away tricks.

Listen to the bidding.

Lead partner’s bid suit unless you have a better suit
yourself. Do not lead declarer’s first bid suit unless you have a solid suit (QJ109) and will not be
giving declarer 3 tricks. In an uncontested auction, lead an un-bid suit.

If you have to choose a suit,
choose dummy’s second bid
suit

Against a slam, lead safe if you
hold cards over declarer’s
suits or attack with a KQ honour sequence in an un-bid suit or a dummy suit.

These are often conflicting
conditions, so expect to get the lead right around 60% only